Specify the architecture for which to generate assembly, overriding the target
encoded in the bitcode file. See the output of llc -help for a list of
valid architectures. By default this is inferred from the target triple or
autodetected to the current architecture.

Specify a specific chip in the current architecture to generate code for.
By default this is inferred from the target triple and autodetected to
the current architecture. For a list of available CPUs, use:
llvm-as < /dev/null | llc -march=xyz -mcpu=help

Override or control specific attributes of the target, such as whether SIMD
operations are enabled or not. The default set of attributes is set by the
current CPU. For a list of available attributes, use:
llvm-as < /dev/null | llc -march=xyz -mattr=help